Fuel injection pump



Feb. 13, 1968 D. E. SHOOK ET AL 3,368,491

FUEL INJECTION PUMP Filed June 22, 1966 2 Sheets-Sheei 1 DAVID E. SHOOKROBERT J. DUNLAP BY INVENTORS.

Feb. 13, 1968 D. E. SHOOK ET AL 3,368,491

FUEL INJECTION PUMP Filed June 22, 1966 2 Sheets-Sheet 2 -7Vndr-qs SfarKe Affomvevs x" 8 m P Mild s ww hm m 3 N u 6 m 432:6 vws su aa ill-15:1,a... I v

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United States Patent C 3,368,491 FUEL INJECTION PUMP David E. Shook andRobert J. Dunlap, Milwaukee, Wis., assignors to Murphy DieselCmpany,-Milwaukee, Wis., a corporation of Delaware Filed June 22, 1966,Ser. No. 559,509 2 Claims. (Cl. 103-41) ABSTRACT OF THE DISCLOSURE Afuel'injection pump of the type employing a plunger in a cylindricalmember having an inlet port and a pressure release port connecting witha'source of fuel, and a pressure relief port in the cylindrical memberdisposed to be uncovered by the plunger 'just ahead of the uncovering ofthe pressure release port.

This invention relates to a fuel injection pump for internal combustionengines generally of the diesel type.

The invention is based upon the discovery that pressure surges in thepump chamber after cut-off and which sometimes cause after dribble infuel injection may be substantially eliminated by providing a minutepressure relief for the pump chamber just ahead of the pressure releaseby the plunger.

The invention avoids the attempts to solve after dribble by specialneedle valve constructions and heavier spring actuated check valves forcontrol of the injection, and makes it possible to employ normal checkvalves with lighter actuating springs.

The accompanying drawings illustrate the best mode presentlycontemplated of carrying out the invention.

In the drawings:

FIGURE 1 is an axial section of a typical fuel injection pump employingthe invention;

FIG. 2 is a transverse section taken through the pump plunger on line 22of FIG. 1;

FIG. 3 is a left side elevation of the lower portion of the pumpplunger;

FIG. 4 is a right side elevation of the lower portion of the pumpplunger;

FIG. 5 is a sectional view similar to FIG. 1 showing the pump plunger inits downward pressure stroke and with the check valves open injectingfuel into the engine cylinder;

FIG. 6 is a view similar to FIG. 5 showing initial opening of the reliefport; and

FIG. 7 is a similar view upon opening of the cut-off port.

Referring to the drawing, the fuel injection pump comprises a hollowgenerally cylindrical body 1 having a pump plunger actuator 2 in one endthereof and a cap or tip nut 3 threaded into the other end thereof.

A tubular cylinder 4 is disposed within body 1 and receives the pumpplunger 5 which reciprocates therein and which has its free endextending upwardly for connection with the actuator 2.

The tip nut 3 contains the valve cartridge 6 which preferably has theconstruction described and illustrated in the copending application ofDavid E. Shook, one of the present co-inventors, Ser. No. 555,545 filedJune 6, 1966 and assigned to a common ass-ignee herewith.

The spacer block 7 of the valve cartridge 6 presses against the adjacentend of cylinder 4 and holds the latter con-fined against an innershoulder 8 of body 1.

The pump chamber 9 is principally formed by the inner end portion ofcylinder 4 and the plunger 5 at one end of the chamber and the spacerblock 7 at the other end of ice the chamber. The chamber 9 has anadditional volume by reason of the connecting axial passage 10, crosspassage 11 and diagonal transfer passages 12 and 13 in plunger '5, andalso by reason of the axial passage through spacer which issubstantially lower than the necessary injection pres-sure, and entersthe body v1 through passage 16 to a cylindrical spacer or chamber 17surrounding the major portion of the cylinder 4 and in directcommunication "with inlet port 15.

A suitable coil spring 18 is carried by body 1 and en gages a flange 19on actuator 2 to bias the latter upwardly and normally maintain plunger5 in its upper position except when being actuated against the springfor injecting fuel into the engine cylinder.

A suitable sleeve 20 may be provided in fuel chamber 17 to prevent undueerosion of the ports and body.

The release port 21 is disposed in cylinder 4 above and on the oppositeside from inlet port 1 5 to discharge directly into the fuel chamber 17at the time for release of the pressure injection, and which is governedby the diagonal transfer passage 1'3 registering with port 21 as theplunger 5 approaches the bottom of its stroke.

Rotational adjustment of plunger 5 as by the rack 22 engaging teeth 23on the upper portion of plunger 5 determines the release time for theinjection.

In carrying out the present invention an initial pressure relief isprovided just ahead of the main release by a small orifice 24 preferablylocated above the inlet port 15 and on the opposite side of plunger 5from release port 21.

The diagonal transfer passage 12 in plunger '5 is disposed on theopposite side from passage 13 and is adapted to uncover relief orifice24 just ahead of the uncovering of release port 21 by passage 13.

Referring to FIGS. 5-7 it will be noted that as plunger 5 movesdownwardly in its charging stroke from the position of FIG. 1, the endof the plunger first cuts off inlet 15, and further movement of theplunger immediately compresses the liquid fuel filling chamber 9,thereby effecting opening of the first check valve 14 and then of thesecond check valve 2 5 as shown in FIG. 5 with a resulting discharge offuel through orifices 26 of tip 27 into the engine cylinder.

As the time for release approaches, the diagonal transfer port 12uncovers orifice 24 and provides a very slight initial pressure reliefprior to final release, as shown in FIG. 6. At this point it is believedthat valves 14 and 2 5 are open but possibly start to close. It may bethat they complete their closing by the time transfer passage 13 startsto uncover release port 21.

In any event, the effect of the initial pressure relief orifice 24 is tosubstantially eliminate the secondary surge in pressure in chamber 9following release and to prevent re-opening of valves 1'4 and 25 withresulting afterdribble. Tests have indicated that this is so regardlessof whether the release is timed to occur at 25%, 50% or of completecharge.

It is believed that the orifice 24 effects a more gradual closing ofcheck valves 14 and 25 which may have some improvement in engineefiiciency by reason of a change in heat release characteristics of theengine. While it has generally been thought that a sharp cut off isdesirable, more recently attempts have been made to vary the cutoff rateby employing release ports of different shapes. Such attempts result inhigh erosion of the port with unpredictable engine performance. Thepresent separate orifice has been found to avoid erosion and to providethe needed control of cut-01f.

Various modes of carrying out the invention are contemplated as beingwithin the scope of the following claims particularly pointing out anddistinctly claiming the subject matter which is regarded as theinvention.

We claim:

1. In a fuel injection pump of the class described having a cylindricalmember with inlet, outlet, leakage collection, and release portsconnecting to a fuel supply and adapted to be covered and uncovered by apump plunger operating within the cylindrical member to provide a pumpchamber at one end, a pressurerelief orifice in said cylindrical memberon a side opposite said release port and also connecting to said fuelsupply, and passage means in the plunger directly connecting said relieforifice to said pump chamber and disposed to uncover said orifice justahead of the uncovering of said release port by the plunger in itspressure stroke.

2. The construction of claim 1 in which said plunger has a separatediagonal transfer passage disposed on the side corresponding to eachsaid release port and said pressure relief orifice, and means torotationally adjust said plunger relative to said member to control thetiming of opening of both said release port and said relief orifice,said diagonal transfer passages being correlated in position furtherapart than the correlation in position between said release port andsaid relief orifice axially of said member to provide a pressure relieffor the pump chamber momentarily prior to cut-off of injection.

References Cited UNITED STATES PATENTS 2,420,164 5/1947 Bremser 103412,521,224 9/1950 Kammer 299107.5 2,551,053 5/1951 Rogers 10341 2,571,50110/1951 Truxell 239 X 2,628,866 2/ 1953 Purchas 23990 2,890,657 6/1959May 103-41 2,985,378 5/1961 Falberg 239--92 X 3,075,707 1/1963 Rademaker23990 3,115,304 12/1963 Humphries 230-90 3,216,359 11/1965 Teichert103-41 DONLEY J. STOCKING, Primary Examiner.

W. J. KRAUSS, Assistant Examiner.

